7.5M views · 65K reactions | The World Trade Center towers were once the tallest buildings in the world. But on 9/11, after being struck by a terrorist attack, they collapsed. Two scientists have thought of a new theory, which may finally explain what happened on that tragic day. The Missing Evidence: 9/11 Secret Explosions in the Towers airs tonight at 10 PM. | Smithsonian Channel | Facebook

Egon Zippel's 9/11 Footage shows the total collapse of the South Tower from West Street. The South Tower (2 WTC) of the World Trade Center was struck by United Airlines Flight 175 at 9:03 a.m. on 9/11, impacting floors 77-85, and collapsed at 9:59 a.m., 56 minutes later, due to the extreme heat from burning jet fuel and office contents weakening its steel structure, leading to progressive collapse and massive casualties, with only a few survivors escaping from above the impact zone. The structur